The objectives of this proposal are to isolate and chemically identify the toxin(s) isolated from the nematocysts of two species of medusae common to the Chesapeake Bay and to determine their specific modes of action using mammalian test systems. One medusa in particular (Chrysaora) is a potent stinger and represents a public health hazard to bathers and fishermen. General toxin properties and their effects on respiratory, cardiovascular and neuromuscular systems, as well as hemolytic capabilities will be evaluated. Where possible, measurements will be made using telemetric instrumentation on unanaesthetized, unrestrained rats so a more accurate analysis can be made. Toxins will also be tested for their ability to release pharmacologically active substances such as histamine, bradykinin and serotonin from mammalian systems.